(CNN) -- Serena Williams successfully defended her Australian Open title with a 6-4 3-6 6-2 victory over Belgium's Justine Henin in a thrilling final in Melbourne on Saturday night.

Top seed and world number one Williams wrapped up victory on her second match point, before falling to the ground in relief as she claimed her 12th grand slam singles title to tie fellow American Billie-Jean King for fifth in the all-time list.

It has been a long-standing ambition for the 28-year-old and it had added resonance as King was watching as a special guest to honor the 40-year anniversary of Australian Margaret Court's four grand slam tournament wins in 1970.

Unseeded Henin, who was attempting to win a grand slam in only her second tournament after a 20-month retirement, threatened to deny Serena her fifth Australian Open with inspired play to win the second set with a run of four straight games but could not force home her advantage.

Williams gained an early break in the decider, only for Henin to hit back for 2-2, but she then strung together a run of four straight games to close out victory with a stinging backhand after just over two hours of intense action on Rod Laver Arena.

Billie we're tied, I've reached my goal--Serena Williams

Henin, attempting to match the feat of compatriot Kim Clijsters, who won last year's U.S. Open on her comeback to competitive tennis, paid for uncertainty on her service with a double fault at 4-5 down in the opener before dumping a forehand into the net to hand Williams the set.

Henin looked in deep trouble when Williams broke to lead early in the second set but she immediately broke back before brilliant play at 3-2 down set her on a run which saw her level at one set apiece.

Now the momentum was with Henin as she won 18 of 19 points, but Williams dug deep to turn the tide in her favor and with a double break there was no way back even for Henin.

The American now has an 8-6 lead in career meetings between the pair, including a 6-2 6-0 win in Miami in 2008, just before Henin retired despite being world number one at the time.